Plasmodium falciparum parasites cause over 1 million deaths from malaria each year and represent one of the most significant public health challenges facing the global community. The secretory pathway of blood- stage P. falciparum parasites plays a key role in mediating the pathology of malaria, transporting cyto-adherent ligands to the surface of infected erythrocytes and erythrocyte invasion ligands to specialized organelles within the parasite. However, many aspect of P. falciparum secretion are poorly understood, particularly the export of proteins to the erythrocyte surface and membrane-bound organelles within the erythrocyte cytosol, a transport step that is unique to P. falciparum biology. Furthermore, fundamental questions about the number and nature of secretory organelles in the P. falciparum pathway remain unanswered. The broad objective of this application is to comprehensively define the basic organization of the P. falciparum secretory pathway and to clarify the role of vesicle targeting in protein transport to membrane-bound organelles that are unique to P. falciparum. t-SNAREs, membrane bound proteins that control the specificity of vesicle fusion, will be used as organelle-specific markers to fill these crucial gaps in our knowledge base. We have identified several putative t-SNAREs in the P. falciparum genome and established that at least one of these is exported to unique organelles that appear in the cytosol of P. falciparum infected erythrocytes and mediate protein transport to the erythrocyte surface. The localization of and targeting signals in P. falciparum t-SNAREs will be investigated under the following specific aims: 1. Establish the sequence and location of the P. falciparum t-SNAREs. 2. Understand the molecular basis ofPfSynS targeting to the Maurer's clefts. An array of molecular, cellular and biochemical tools will be used to complete these aims, including immunofluorescence microscopy, sub-cellular fractionation and epitope tagging. This research is significant because it will be the first study of t-SNAREs and vesicle targeting in P. falciparum and may help clarify long- standing disputes about the basic structure of the P. falciparum secretory pathway. By focusing on elements of P. falciparum secretion that are unique to this organism, we aim to identify targets for the future development of novel prevention and control measures. [unreadable] [unreadable] [unreadable]